Risk Genes For Alzheimer’s Disease
The vast majority of people with Alzheimer’s disease do not inherit it from a parent as a single-gene mutation with a simple inheritance pattern. Instead, the inheritance follows a more complex pattern. The disease might skip a generation, affect people on both sides of the family, appear seemingly from nowhere or not be passed on at all.
More than 20 gene variants have now been identified which affect – to different degrees – the chances of a person developing Alzheimer’s disease. The effects of these genes are subtle. Different variants act to slightly increase or decrease the risk of a person developing Alzheimer’s disease, but do not directly cause it. These ‘risk genes’ interact with each other and with other factors, such as age and lifestyle, to influence someone’s overall risk of getting the disease.
Genes And Frontotemporal Dementia
Frontotemporal dementia , originally called Picks disease, is a rarer type of dementia mostly affecting people under the age of 65 years. The symptoms of FTD can be quite varied but include changes that mostly affect behaviour or language. There are different types of FTD, and these are likely to have different causes.
Some people with FTD have a family history of dementia and the condition may be inherited in some of these families. For behavioural variant FTD, a third to half of people could have a family history. This figure is thought to be much lower for other types of FTD.
Overall, around one in ten cases of FTD are thought to be caused by a faulty gene passed down in families. Several genes have been found that can cause these inherited types of FTD, including:
Mutations in the MAPT gene can cause the tau protein to behave abnormally, forming toxic clumps that can damage brain cells. We still need to understand more about how mutations in progranulin and C9ORF72 cause the disease.
The C9ORF72 gene can cause people to develop motor neurone disease, FTD or both conditions, and may affect members of the same family differently.
In cases of FTD that are not caused by faulty genes, the risk factors are not yet fully understood, and research is ongoing.
Is genetic testing available for frontotemporal dementia?
Genetics: One Contributor To Addiction
It has been found that genetics can play a role in the development of addiction. Genes may contribute to the vulnerability to substance abuse in a number of ways: genetic mutations that lead to alterations in the structure and function of the brain may influence the way in which the individual responds to exposure to the substance.6For example,the gene aldehyde dehydrogenase 2 has been known to be a protective factor of alcohol dependence by affecting the way that alcohol is broken down in the body. Moreover, individuals may be genetically more likely to exhibit problems with impulsivity, poor emotion regulation skills, executive dysfunction, or other temperamental characteristics that may increase their individual risk for using substances.7
While certain genes have been proposed to contribute to addiction, including the interaction of multiple genes, it is uncertain whether a true genotype of addiction can ever been discovered, due to the complex personality and environmental factors that also shape addiction.20
Testing For Familial Alzheimers Disease
The decision to undergo testing for FAD is very complex and the advantages and disadvantages must be carefully considered. The test does not produce a relative risk of acquiring the dementia, but is a definitive prediction of whether a person will get a profound and progressive illness in ones middle years. The test can only be completed with the informed consent of the person being tested. No one should ever be pressured to have such a test.
Knowing that you are carrying the gene may help some people plan for the future. It enables them to consider future lifestyle choices and to let their wishes be known to someone they trust. However, given that no cure is available an individual has to consider whether they want to know that they will develop dementia at some time in the future.
To help people consider these issues specialised genetic counselling is essential. The doctor can provide details of this service. In the future, when preventive treatments for Alzheimers disease become available, there may be increased reasons to seek testing.
Causes Of Alzheimers: Is It Hereditary
Increasing cases of Alzheimers disease
The Alzheimers Association states that Alzheimers disease is the sixth leading cause of death in the United States, and that more than 5 million Americans are affected by the condition. Additionally, one out of three seniors dies of Alzheimers or some other type of dementia. That number will likely increase as the aging population increases.
Scientists have been researching Alzheimers for decades, but still there is no cure. Learn more about how genes are related to the development of Alzheimers, as well as other potential causes of the condition.
Alzheimers And Inheritable Traits
Just how likely are family members of those with Alzheimers to get the disease themselves? People think that if Dad and Mom or an aunt or uncle had Alzheimers, they are doomed. But, no, thats not true, says Dr. Gad Marshall, assistant professor of neurology at Harvard Medical School.
Even though family history adds to the overall risk, age still usually trumps it quite a bit. It means your risk is higher, but its not that much higher if you consider the absolute numbers.
As Dr. Marshall notes, the most common form of the disease is age-related Alzheimers, which means the risk of the disease comes from a persons age and not their genetic predisposition. The older a person is, the higher risk they have of getting Alzheimers, and this pertains to everyone, whether theyve had a family member with the disease or not.
The statistics show that after age 65, everyone develops a 2% increased risk per year of getting diagnosed with Alzheimers. Other Harvard Health statistics show that:
Family Tree Of Gene Inheritance
This diagram represents a family tree showing strong inheritance of a mutation across three generations.
In this scenario, the affected grandfather had three children. Two of the three children inherited the mutation. Of these two, the daughter has one affected male child and the affected son has no children. The two children of the unaffected son are free of the mutation.
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Family History By The Numbers
Studies of family history say that if you have a close relative who has been diagnosed with Alzheimer’s diseasethe most common form of dementia in older adultsyour risk increases by about 30%. This is a relative risk increase, meaning a 30% hike in your existing risk.
If you are age 65, the risk of being diagnosed with Alzheimer’s is 2% per year, although this also means a 98% chance per year of not developing Alzheimer’s. In absolute numbers, a 2% annual risk means that two out of 100 65-year-olds will develop dementia every year.
Family history raises the 2% annual risk by about 30%, to 2.6% per year. That means going from 20 cases in a group of 1,000 to 26 in 1,000, or six additional cases in 1,000. “So the absolute increase is relatively small,” Dr. Marshall says.
Age raises the chance of Alzheimer’s more than family history. People in their 70s have a 5% chance of being diagnosedmore than twice that of people in their 60s. Family history raises this by 30%, from 5% to 6.5%. Again, the absolute change is relatively small.
Addiction In The Household: What It’s Like In A Drug And Alcohol Home
While genetics are a critical the environment also plays an important role in this risk. growing up with a parent or parents who are addicted to substances may influence one’s vulnerability to the disorder.
Families with one or more parent suffering from addiction are often difficult to live in and lead to abnormal degrees of stress.14, 15 There are generally few normal routines in these families, making day-to-day life unpredictable. Further, parents with addiction likely exhibit intense mood swings and erratic behavior. 16 Children are often exposed to traumatic and intensely stressful experiences, and may develop patterns of anxiety or even ambivalence in response to this chronic stress and unpredictability. 17 Child abuse is also more prevalent in families of an addicted parent. 16
Some studies have suggested that children of addicted parents struggle with feeling overwhelmed by very strong emotions. 17 This is likely because the stressful experiences as a result of the addiction environment impeded their emotional development. Moreover, these children lack appropriate familial support and guidance in terms of learning how to appropriately regulate their emotional responses to situations in order to deal with them. They will often default to responding with defensiveness to intense emotion, including shutting down, withdrawing, intellectualizing, rationalizing, acting out, or self-medicating. 18
Lifestyle And Genetics Both Play A Small Role In Dementia
The lifestyle score was associated with dementia risk. Second, the genetic score was also associated with dementia. In other words, individuals with worse scores were at higher risk for dementia. The researchers further found that genetic risk and lifestyle appeared to act independently of each other. For example, individuals with both an unhealthy lifestyle and a high genetic risk score had almost two and a half times more risk than individuals with a low genetic score and healthy lifestyle.
However, this research was not designed to prove whether lifestyle and environment or genes cause dementia. A lot more could explain the differences between people who develop dementia. If populations at high genetic risk changed their lifestyle, and if the lifestyle was known to be the cause of AD , one out of 121 dementia cases would be prevented in 10 years. This is significant, but what number of lifestyle modifications would it take for the prevention of AD in 10, 50, or even 120 people? Do genetics even matter?
Second, the genes and lifestyle did not appear to work together or they werent synergistic in dementia risk. Specifically, this means that individuals with both bad genetic and lifestyle scores were not at risk for developing dementia any more than the sum of the parts or the individual scores alone.
Alzheimer’s Disease And Alzheimer’s Dementia
Alzheimer’s disease is not usually hereditary. It is therefore not generally caused by the genes received from a person’s parents. Even if several members of a family have in the past been diagnosed with Alzheimer’s disease, this does not mean that another member of the family will necessarily develop it, as the majority of cases of Alzheimer’s disease are not genetic. However, as the disease is so common amongst older people, it is not unusual for two or more family members over the age of 65 to have it.
Whether or not there are other members of a family with Alzheimer’s disease, everyone risks developing the disease at some time. However, it is now known that there is a gene, which can affect this risk. This gene is found on chromosome 19 and it is responsible for the production of a protein called apolipoprotein E . There are three main types of this protein, one of which , although uncommon, makes it more likely that Alzheimer’s dementia will occur. However, it does not cause the condition but merely increases the likelihood of developing it. For example, a person of 50, would have a 2 in 1,000 chance of developing Alzheimer’s dementia instead of the usual 1 in 1,000, but might never actually develop it. Only half of people with Alzheimer’s dementia have ApoE4 and not everyone with ApoE4 has it.
What To Do If Someone In Your Family Is Diagnosed With Alzheimer’s
Contact the Alzheimer’s Association . Find out about resources available to help you and your family. State and county agencies may also be able to help.
Plan for the future. This includes legally designating someone to make health care and financial decisions for the affected person when he or she can’t.
Investigate long-term care options. Nursing care is expensive, and finding a good place can take time. Start early.
Take care of physical health. People with dementia who live a healthy lifestyle tend to progress more slowly to the later stages.
Steer away from genetic testing. Even if you have the APOE Alzheimer’s risk gene, it usually doesn’t mean you will develop dementia later in life.
Risk Genes For Frontotemporal Dementia
In the past few years, researchers have begun to look for ‘risk genes’ for FTD. For example, variants in a gene called TMEM106B affect someone’s chances of developing FTD.
How can I help with research?
Many dementia research studies rely on the participation of volunteers. See whether you can take part.
Exercise Your Body And Mind
Physical exercise is an important part of a healthy lifestyle, and some studies suggest that it can improve cognitive agility. For an Alzheimers patient, exercise may also help maintain muscle strength, decrease frailty, and elevate mood.
Some research suggests that exercising our brain, through activities like reading, learning a musical instrument, or playing chess, can help protect people from cognitive decline later in life. Again, rigorous clinical trials will be required to prove this is true. In the meantime, learning new skills and activities may, at a minimum, enrich your life. Learn more about healthy living with Alzheimers disease.
Differential Diagnosis Of Alzheimer Disease
Differential diagnosis of AD includes other causes of dementia, especially treatable forms of cognitive decline, such as depression, chronic drug intoxication, chronic central nervous system infection, thyroid disease, vitamin deficiencies , central nervous system angitis, and normal-pressure hydrocephalus.
Other degenerative disorders associated with dementia, such as frontotemporal dementia, including frontotemporal dementia with parkinsonism-17, Picks disease, Parkinson disease, diffuse Lewy body disease, Creutzfeldt-Jakob disease, and cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy , may also be confused with AD.
Computerized tomography and magnetic resonance imaging are valuable for identifying some of these other causes of dementia, including neoplasms, normal-pressure hydrocephalus, frontotemporal dementia, and cerebral vascular disease.
Risk To Family Memberslate
Genetic counseling for people with nonfamilial AD and their family members must be empiric and relatively nonspecific. It should be pointed out that AD is common and that the overall lifetime risk to any individual of developing dementia is approximately 1012%.
First-degree relatives of a person with AD have a cumulative lifetime risk of developing AD of about 1530%, which is typically reported as a 2025% risk., This risk is about 2.5 times that of the background risk .,
Disagreement exists as to whether the age of onset of the affected person changes the risk to first-degree relatives. One study found that early-onset AD increased the risk, whereas another study did not.
The number of additional affected family members probably increases the risk to close relatives, but the magnitude of that increase is unclear unless the pattern in the family is characteristic of autosomal-dominant inheritance. Having two, three, or more affected family members probably raises the risk to other first-degree relatives in excess of that noted above for nonfamilial cases, although the exact magnitude of the risk is not clear. Heston et al. found a 3545% risk of dementia in individuals who had a parent with AD and a sib with onset of AD before age 70 years. Jayadev et al. also report data suggesting that offspring of parents with conjugal AD had an increased risk of dementia.
Your Genes Can Increase Your Risk For Dementia
Having a family memberespeciallya first-degree relative like your mother, father, sister, or brotherwithsevere memory problems, Alzheimers disease, or another form of dementia makesyou 3.5 times more likely to develop symptoms. Similarly, if you have one ortwo copies of the APOE4 gene, you have a greater chance of memory problems.
Many people in the medical community contend that there is nothing anyone can do to mitigate genetic risk. Theyre wrong. There are many things you can do to reduce your risk even if you have a genetic predisposition for the disease. Just look at Bud.
The Role Of Genetics: Will I Get Alzheimers Disease
Scientists are still trying to determine the underlying causes of Alzheimers disease. The hope is that one day we will be able to stop the disease from progressing or perhaps even prevent it altogether. To date, researchers have identified a few genes that play an important role in Alzheimers. Some of these genes are simply risk factors for Alzheimers disease. Other genes are hereditary and will cause Alzheimers disease to develop.
There are two types of Alzheimers disease: early-onset Alzheimers disease and late-onset Alzheimers disease. Early-onset Alzheimers disease is rare, occurring in people age 60 and younger. This represents less than 5% of all people with Alzheimers. One type of early-onset Alzheimers disease is known as autosomal dominant Alzheimers disease or early-onset familial Alzheimers disease . This is even more uncommon, affecting less than 1% of all people with Alzheimers. What makes this type of early-onset Alzheimers disease so unusual is that it is caused by a hereditary genetic mutation to one of three genes PSEN1, PSEN2, or APP.
A recent study examined data from 4 large, observational studies of adults ages 60 and older. The study reported the association between various APOE genotypes and the risk of developing mild cognitive impairment or dementia due to Alzheimers by age 85 as follows:
- No family history of dementia
- Being male
Factors that may increase a persons risk of developing Alzheimers include:
Your Genes Are Not Your Destiny
Studies show that our genetics predict only about 20-30% of our longevity. The rest is up to our lifestyle choices. Its similar for dementia risk. When Bud saw his brain scans and his cognitive testing results, he got serious about his physical health and his brain health. He completely overhauled his dietdramatically reducing his sugar consumption, increasing his intake of protein and healthy fats, decreasing the number of processed carbohydrates, and adding important nutritional supplements. He also started exercising and began using a CPAP machine to help his sleep apnea.
Within a year, he dropped 30 pounds and was happy to seeblood pressure and blood sugar levels fall into a healthy range. Even better,he said his memory and focus were better than when he was in his 20s. Withthese lifestyle changes, Bud had lowered his risk for the dreaded disease. Youcan do it too.
Do Genes Cause Diseases
Genetic mutations can cause diseases. If a person inherits a genetic mutation that causes a certain disease, then he or she will usually get the disease. Sickle cell anemia, cystic fibrosis, and some cases of early-onset Alzheimer’s disease are examples of inherited genetic disorders.
Other changes or differences in genes, called genetic variants, may increase or decrease a person’s risk of developing a particular disease. When a genetic variant increases disease risk but does not directly cause a disease, it is called a genetic risk factor.
Identifying genetic variants may help researchers find the most effective ways to treat or prevent diseases such as Alzheimer’s in an individual. This approach, called precision medicine, takes into account individual variability in genes, environment, and lifestyle for each person.
The expression of geneswhen they are switched on or offcan be affected, positively and negatively, by environmental and lifestyle factors, such as exercise, diet, chemicals, or smoking. The field of epigenetics is studying how such factors can alter a cell’s DNA in ways that affect gene activity.
Six Common Health Conditions That May Be Inherited
Some inherited traits are obvious like your mothers bright-blue eyes or your fathers dimples. But some health conditions have a surprising genetic component that you may not be aware of. Here are six common health conditions that run in the family, and how you can work with your doctor on effective treatment plans.
Can You Inherit Alzheimers
Finding out that someone you love has Alzheimers can be frightening. Its natural to worry about their future and also to have concerns that you may inherit the disease, or pass it on to your children.
We dont fully understand the factors that cause Alzheimers disease. Your lifestyle, your environment, and your genetic heritage may all have an impact on whether you develop Alzheimer’s dementia.
Genetic Testing Not Helpful
When a relative is diagnosed with dementia later in life, family members often wonder if they should be tested for the “Alzheimer’s gene.” The short answer is no. “It can be a quick no or a long no, with more explanation, but the answer is nearly always no,” Dr. Marshall says. “It’s not going to be helpful, since it won’t tell you whether you will develop the disease. It will only tell you if you are at a greater or lower risk.”
For Alzheimer’s disease that begins later in lifethe vast majority of casesa gene called apolipoprotein E is associated with greater risk for dementia. If you inherit one copy of APOE4, your risk triples. If you have two copies, your risk is 10 to 15 times higher .
But having APOE4 does not mean you will definitely develop dementia. Among people who age normally into their 70s, about 25% still have one or more copies of the risk gene. Nor does the absence of APOE4 protect you: about 35% of people with Alzheimer’s don’t have one of the risk genes.
This means that if genetic testing reveals that you have one or more copies of APOE4, it will not tell you what you really want to know: will you definitely get Alzheimer’s diseaseor will you not? Knowing that you have the risk gene could instill fear and negatively influence your life decisions.
Related Genetic Counseling Issues
Use of APOE genotyping for predictive testing
In contrast to the use of APOE testing as an adjunct diagnostic test in individuals with dementia, there is general agreement that APOE testing has limited value used for predictive testing for AD in asymptomatic persons. Data suggest that a young asymptomatic person with the APOE e4/e4 genotype may have an approximately 30% lifetime risk of developing AD. Further refinement of this risk reveals that women with an APOE e4/e4 genotype have a 45% probability of developing AD by age 73 years, whereas men have a 25% risk. These risks are lowerand the likely age of onset laterfor persons with only one APOE e4 allele or no APOE e4 allele . These estimates are not generally considered clinically useful; however, a research study to assess the potential use of APOE testing in relatives of individuals with late-onset AD is under way.,
Family members of persons with DS are not at increased risk for AD.
Your Risk Of Dementia: Do Lifestyle And Genetics Matter
Globally, Alzheimers disease and other forms of dementia are a major burden on individuals and communities. To make matters worse, there are few treatments to combat these complex illnesses. Even the causes of dementia are widely debated. Sadly, clinical trials for drugs to stop or even slow its progress have come up short. Taking a different tack, some experts hope to intervene before people are diagnosed with dementia by encouraging lifestyle changes.
Alzheimer’s Disease Inherited Through Maternal Line Study Finds
- A family history of Alzheimer’s disease significantly increases the risk for developing this disorder, but a new study suggests that which of your parents has the disease is very important.
A family history of Alzheimer’s disease significantly increases the risk for developing this disorder, but a new study in Biological Psychiatry suggests that which of your parents has the disease is very important.
Alzheimer’s is the most common form of dementia in late-life, affecting over 5 million elderly in the United States alone. In order to develop preventative treatments, it is necessary to identify those individuals who are at highest risk for developing Alzheimer’s.
Although individuals with a parental history of Alzheimer’s are at increased risk for developing the disease, the specific biological and genetic mechanisms accounting for this increased risk are not known.
An important consideration may be a phenomenon called genomic imprinting, where the pattern of the inherited disease differs based on whether the risk genes are inherited from the mother or the father. Imprinting is a type of epigenetic regulation, meaning that long lasting changes in gene function are produced through regulatory mechanisms rather than by altering the sequence of the DNA.